The P2P model has many potential advantages (e.g., large scale,
fault-tolerance, low cost of administration and maintenance) due to the design
flexibility of overlay networks and the decentralized management of cooperative
sharing of information and resources. However, the mismatch between the
randomly constructed overlay network topology (combined with its
broadcast-style message forwarding infrastructure) and the underlying packet
routing introduces difficult performance problems, exemplified by the Short-Cut
Effect. This paper presents two peer-to-peer (P2P) system-level facilities to
address the problems. First, we propose a capability-aware mechanism to
structure the overlay topology in the form of layers that takes peer
heterogeneity into account. Second, we develop a Probabilistic Broadening
search technique, empowered with capability-sensitive query forwarding scheme
which integrates gracefully with result caching techniques to improve the
search performance of a P2P!
system. We believe that efforts on bridging the gap (mismatch) between
overlay networks and underlying Internet will bring P2P services beyond pure
``best effort'' and closer to serious applications with quality of service
requirements.